The present invention relates to a camshaft which has improved bending resistance and, more particularly, to a camshaft having a barrel-shaped shank portion between a pair of cams, with a maximum diameter in the middle region of the shank portion equal to or less than the base circle of the cams.
A camshaft is described in German Offenlegungsschrift 2,213,224 for the purpose of increasing the design strength of the camshaft. To do so, a continuous transition to the functional faces of the cam and of the bearing point is provided, but with varying cross-sectional forms with essentially straight generatrices of the shank portions being obtained. Due to the non-circular cross-sectional forms even next to the cams, a camshaft of this type can be produced and machined only at a considerable expense, and in particular lateral constrictions also make the machining of the functional faces by grinding more difficult.
Furthermore, a camshaft is described in German Auslegeschrift 1,910,517, in which non-cylindrical shank portions located between two cams and between these and a bearing point have contours curved inwards, as seen in elevational view.
An object of the present invention is to provide a camshaft of high rigidity, which is simple to produce and the machining of which, especially of the functional faces such as the cams, is not made difficult and is not restricted by the shank portions.
According to the present invention, the foregoing objects are achieved by providing non-cylindrical shank portions to connect bearing points with cams, in which shank portions between two cams are barrel-shaped with a maximum diameter located on the middle region of the barrel-shaped shank portions. Also, frustoconical shank portions are formed between a cam and a bearing point.
The camshaft according to the present invention has relatively large diameters in the shank portions between the cams and therefore a high bending resistance. At the same time, those regions of the shank portions near the cams are set back or undercut to such an extent that the machining and chamfering of the cam faces, for example by shaping grinding, are not impaired, with the necessary clearance for the grinding wheels being ensured.
By virtue of the present invention, there is no possibility of grinding down the shank portions, thereby initiating a notch effect which reduces the rigidity of the camshaft. Since the shank portions preserve an overall circular cross-sectional form everywhere, it is possible for them to be produced and machined at a low cost.
As seen in an elevational view, the middle region of the barrel-shaped shank portions between two cams has the shape of an arc defined by a circle which has a radius of curvature on the order of magnitude of the base circle of the cam. This configuration assures high bending resistance and keeps the cams free for machining.
The frustoconical shank portions between a cam and bearing point ensure an increased bending resistance of the shank portions between the cams and the bearing points and therefore of the camshaft as a whole, without impairing access to the cam faces and the bearing points for machining purposes and without departing from the circular cross-sectional form of the shank portions.
These and other features, objects and advantages of the present invention will become more apparent from the following detailed descriptions of a presently preferred embodiment when taken in conjunction with the accompanying drawings.